Structure of a laser beam scanner for a photosensitive printing device

摘要

In a laser scanner device in which a laser beam emitted from a laser diode is reflected in a main scan direction over a predetermined angle by a polygon mirror which rotates at a high speed, the laser beam is reflected from a flat mirror and received by a horizontal synchronizing detection sensor before the laser beam enters a scanning region in which a main scanning operation of the laser beam is performed to form an electrostatic image on a photosensitive drum. In response to the detection of the laser beam, the detection sensor produces a horizontal synchronizing signal which is used as a reference phase to determine a start phase of the main scanning operation. The laser diode and the horizontal synchronizing detection sensor are disposed proximate to each other so that the first optical axis of the laser beam emitted from the laser diode is located at an angle-retarded side in the rotational direction of the polygon mirror with respect to the second optical axis of the laser beam which is reflected from the polygon mirror and then enters the horizontal synchronizing detection sensor. In addition, the laser diode and the horizontal synchronizing detection sensor are mounted on the same board.